There is an ongoing demand for improved surgical devices that are capable of removing objects from a patient's body. In the fields of urology and gastroenterology, for example, improved devices are needed for capturing and retrieving calculi (or “stones”) formed in the urinary tract. Calculi deposits commonly are composed of calcium oxalate. Calculi cause pain, whether they are positioned in the kidney or bladder, or elsewhere, and they can be especially painful as they pass through a duct, such as the ureter. Calculi often need to be removed surgically to alleviate pain, urinary obstruction, or possible infection.
Various retrieval baskets have been proposed over the years for calculi removal. They generally include wires formed to define a “cage” in an expanded position into which calculi can be maneuvered. A sheath may be provided to maintain the wires in a collapsed position for insertion. A handle may be provided for manipulation of the sheath and basket with respect to one another in order to move the basket or cage between the collapsed and expanded positions. A conventional helical style basket is typically used for capturing calculi from the patient's duct, while a conventional straight wire basket is typically used for capturing calculi from the patient's Kidney calyx.
For patient duct calculus retrieval's, the basket is advanced distally to a position within the patient's duct that is beyond a calculus to be grasped while the basket is in the collapsed position within the sheath. It is subsequently expanded upon release from the sheath and drawn back proximally to capture the calculus.
For kidney calyx calculus retrieval's, the basket is advanced to a position within the patient's kidney just proximal to the calculus while the basket is in the collapsed position within the sheath. The basket is subsequently expanded upon release from the sheath, advanced into the calculus, and if necessary, rotated using device handle) to capture the calculus.
Conventional retrieval baskets typically have wire members that are gathered and fastened together into a tube forming a tip extension 2. The tip extension follows the long axis of the basket. An example of a conventional straight wire device with an extended tip is shown in FIGS. 1 and 2. Conventional devices have a tip extension distance d typically of 5-8 mm. The rigid tip extension 2 may cause patient discomfort, bleeding—which not only may be injurious, but can blur the physician's working field of vision—or patient trauma when advanced into certain kinds of tissue, including mucosal tissue. The extending tip is also a design disadvantage in many stone capture attempts (especially for calyceal stones) because the extended tip encounters structures so that basket wires are hindered or prohibited from reaching the distal side of the stone.
In addition to the disadvantages of an extended tip, conventional means for securing the distal end of a basket may hinder the operation of the basket. For example, the opening and closing of the basket wires may be suboptimal, depending on how the wires are secured to form the distal end of the basket.
In the prior art, attempts have been made to provide tipless baskets. Wittich, et al., U.S. Pat. No. 5,057,114 and Cope, et al., U.S. Pat. No. 5,064,428 each disclose a basket without an extending tip. Wire loops in the basket are secured together at their distal end via a suture treated with a urethane coating material. Foster, U.S. Pat. No. 5,989,266 also discloses a basket without an extending tip. In this case, a small wire loop is formed in a first of two larger basket wires. At the distal end of the basket, the second of two wire loops passes through the smaller loop to interlock the larger wire loops together and to form a tipless basket. Accordingly, apart from sutures and wires, the tipless baskets of the prior art do not involve any structural body combined with wires. Given reliability and safety issues inherent in medical procedures, there is a strong demand for tipless retrieval devices that have improved strength and integrity.
There are significant disadvantages in the foregoing approaches for forming a tipless basket. For example, the wires at the distal tip are either self-securing or secured by suture materials. These methods provide baskets of questionable strength and/or integrity. Further, the tipless devices of the prior art may be prone to rapid wear or degradation in use or in sterilization procedures (if the device is a non-disposable). Further, the use of interlocking wires may compromise the shape and integrity of the basket because the wires may move relative to each other given the nature of a loop or suture. The process of assembling the basket may also be complicated by the nature of the foregoing construction and materials. For example, the foregoing tipless prior art baskets are not known to be suitable for use in helical wire baskets. Helical baskets provide improved grasping and release functionality relative to convention basket arrangements. It is questionable whether the looping or suturing methods would be suitable for forming and maintaining the demanding configuration of a helical basket. Further, the foregoing tipless prior art baskets are known to have difficulty capturing and retaining calculus. Accordingly, there is a need for tipless baskets that provide improved grasping, retention and release functionality relative to conventional basket arrangements. For at least the foregoing reasons, there is a need for improved means of securing the distal ends of a medical retrieval basket. More particularly, there is a need for improved tipless retrieval baskets.